title: Oxidative stress reduces Na+/H+ exchange (NHE) activity in a biliary epithelial cancer cell line (Mz-Cha-1).
abstract: In cholangiocarcinogenesis, chronic inflammation and oxidative stress play a key role. The Na(+)/H(+) exchanger (NHE) forms a potential link between control of intra- and pericellular pH and tumor development. Therefore, the effects of oxidant stress were determined by the use of tert-butyl hydroperoxide (t-BOOH) on Na(+)/H(+) exchange in a biliary epithelial cancer cell line (Mz-Cha-1). The cells were exposed to the hydroperoxide and the rate of recovery from acidosis was determined by the use of the pH-sensitive fluorochrome 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester (BCECF/AM). t-BOOH reduced Na(+)/H(+) exchange activity in a dose-dependent manner. At 4 mM t-BOOH, Na(+)/H(+) exchange activity was virtually absent. This was accompanied by an increase in cytotoxicity (MTT assay). Glutathione repletion and intracellular Ca(++) chelation partially restored the Na(+)/H(+) exchange activity. Hydroperoxide seemed neither to alter the intracellular signal transduction pathways (cAMP and Ca(++) oscillations) nor the membrane distribution of the exchanger (immunostaining). Decrease in Na(+)/H(+) exchange activity in this model of oxidant stress may represent an early perturbation of membrane function, and the functional integrity of Na(+)/H(+) exchange could therefore be dependent on the glutathione redox system.
authors.affiliation: Department of Gastroenterology, St Elisabeth Hospital, PO Box 580, 46225 Dorsten, Germany. dr.c.elsing@kkrn.de
authors.forename: Christoph
authors.initials: C
authors.lastname: Elsing
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Voss
authors.forename: Thomas
authors.initials: T
authors.lastname: Herrmann
authors.forename: Iris
authors.initials: I
authors.lastname: Kaiser
authors.forename: Chrisitan A
authors.initials: CA
authors.lastname: Huebner
authors.forename: Thorsten
authors.initials: T
authors.lastname: Schlenker
mesh_terms: D000138:Acidosis / Q000378:metabolism; D001650:Bile Duct Neoplasms / Q000378:metabolism*; D001653:Bile Ducts, Intrahepatic / Q000378:metabolism* / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D027682:Cation Transport Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000494:pharmacology; D018281:Cholangiocarcinoma / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005452:Fluoresceins / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D015514:Oncogene Proteins, Fusion / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D020122:tert-Butylhydroperoxide / Q000494:pharmacology
chemical_list: D027682:Cation Transport Proteins; D002614:Chelating Agents; D005452:Fluoresceins; C489427:MYC protein, human; D015514:Oncogene Proteins, Fusion; D016271:Proto-Oncogene Proteins c-myc; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; C057433:2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester; D020122:tert-Butylhydroperoxide; D000242:Cyclic AMP; D005978:Glutathione; D002118:Calcium